Sorry I was going by the manual, the manufacturer links to a manual for the 30 not the 30i. It seems to have a slightly different user interface http://razorweld.com/userfiles/file/Vipercut%2030%20Manual.pdf
page 8 and 9. It’s the toggle switch on the left.
If your plasma interface doesn’t look like that perhaps this thread will help:
If you purchased the Razorweld Vipercut 30i from our website, this machine only utilizes 2T mode.